Heating unit



FIG. 1 is a perspective view of the heating unit embodying my design;

FIG. 2 is an alternate perspective view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a back view thereof;

FIG. 6 is a right end view thereof;

FIG. 7 is a left end view thereof; and,

FIG. 8 is a bottom view thereof.

The ornamental design for a heating unit, as shown and described.